1. Technical Field
The present invention relates to a rotary-drum type magnetic separator that separates and recovers sludge contained in used coolant. More particularly, the present invention relates to a rotary-drum type magnetic separator that can prevent sludge from remaining in a flow passage formed near both end portions of a rotary drum that rotates.
Priority is claimed to Japanese Patent Application No. 2012-050156, filed Mar. 7, 2012, the entire content of each of which is incorporated herein by reference.
2. Description of the Related Art
Scraps, chips, and the like, which are discharged together with used coolant in the cutting, grinding, and the like of magnetic materials typified by metal materials, particularly, steel materials, are separated from a liquid component and recovered. Since the scraps, chips, and the like have various shapes, various magnetic separators (recovery devices) have been developed in terms of recovery efficiency.
For example, a rotary-drum type magnetic separator in the related art is disclosed. FIG. 1 is a cross-sectional view, which shows the structure of the rotary-drum type magnetic separator in the related art, taken along a plane orthogonal to the rotating shaft of a rotary drum. As shown in FIG. 1, the rotary-drum type magnetic separator in the related art includes a liquid storage portion 10 that is provided in a box-shaped body 1 and stores used coolant. A rotary drum 3 is supported near the middle portion of the body 1 so that the liquid storage portion 10 is divided into two portions and the rotary drum 3 can be rotated in a substantially horizontal direction. The rotary drum 3 is a cylindrical body that is made of a non-magnetic material such as stainless steel. An inner cylinder 5, which includes a plurality of magnets 4 disposed on the outer peripheral surface thereof in a predetermined arrangement, is coaxially fixed in an outer cylinder by a rotating shaft 31. The polarities of the plurality of magnets 4 are disposed to generate a predetermined magnetic flux near the outer peripheral surface of the rotary drum 3 so that the plurality of magnets 4 magnetically attract scraps, chips, and the like that are magnetic materials contained in the used coolant.
In the related art, the plurality of magnets 4 are disposed between a portion of the rotary drum 3, which is immersed in the liquid storage portion 10, and the top portion of the rotary drum, that is, on a portion of the inner cylinder 5 corresponding to a portion corresponding to about three quarters of the outer peripheral surface of the rotary drum 3. The magnets 4 are not disposed on the remaining portion of the inner cylinder 5 corresponding to about one quarter so that a magnetic force is not applied to the remaining portion of the inner cylinder.
Sludge, which is attracted to the outer peripheral surface of the rotary drum 3 at the bottom of the liquid storage portion 10 by the action of the magnetic forces of the plurality of magnets 4, is conveyed to the top portion of the rotary drum 3 with the rotation of the rotary drum 3. The conveyed sludge is released from the attractive forces, which are caused by the magnetic forces of the plurality of magnets 4, when passing through the top portion. Then, the conveyed sludge is scraped by a scraper 7, which comes into contact with the surface of the rotary drum 3, and is recovered. A squeezing roller 6, which is provided with an elastic body such as rubber on the surface thereof, is provided near the top portion of the rotary drum 3, and comes into contact with the outer peripheral surface of the rotary drum 3 at a predetermined pressure. While the attracted sludge passes between the rotary drum 3 and the squeezing roller 6, a liquid component contained in the sludge is squeezed. Then, only scraps, chips, and the like are separated at a position where a magnetic force is not applied.